When foreign substances such as water, dust, or the like intrude into an electronic device from the outside, electronic components on a circuit board disposed in the electronic device may be short-circuited, causing serious failures. Thus, it is preferred that the openings formed on the casing of the electronic device is reduced to be minimal in order to prevent foreign substances from intruding inside.
However, in some cases, it is required to form an opening on a casing of an electronic device due to the configuration of the casing. For example, an opening may be needed to mount another component to the electronic device, or an opening may be needed for heat dissipation of the electronic device.
Thus, Patent Literature 1, for example, discloses a structure of a drop prevention wall that is provided with a terminal block placed in a casing of an inverter. The drop prevention wall prevents foreign substances from further intruding beyond the terminal block, when they intrude through a service hole formed on the casing to access to the terminal block.